This invention relates to a method and apparatus which uses a sheet of fabric to hold a cementitious slurry during casting of a concrete structure.
Fabric containers have previously been used to hold cementitious slurry during the forming of a cast-in-place concrete structure. These fabric containers have been supported by tubular frameworks which engage the outer side surface of the fabric and are disposed outside of the resulting concrete structure. Upon solidification of the slurry, the outside framework is removed. The forming of concrete structures in this manner is disclosed in U.S. Pat. No. 3,726,950.
The aforementioned patent also discloses the use of support structures which are disposed on the inside of a slurry receiving cavity defined by the fabric. When inside supports are used, wire or other tension-restraining tie-elements extend through the sheet of fabric to hold the fabric in place relative to the support structure. Since the wire tie-elements extend through the fabric sheet, they project outwardly from the resulting concrete structure and provide a path for corrosion. In addition, the tie elements may tend to concentrate stresses in the sheet and weaken the sheet.